Zinc(II)‐poly(urea‐formaldehyde) supported on magnetic nanoparticles: A hybrid nanocatalyst for green synthesis of spiropyrans, spiroxanthenes, and spiropyrimidines

Abstract

Immobilization of metal ions onto inorganic supports has very interesting biological, industrial, and catalysis applications. In this study, CoFe2O4@SiO2@PUF@Zn(OAc)2 nanostructure was successfully fabricated by immobilization of zinc acetate on the surface of poly(urea‐formaldehyde) supported on magnetic CoFe2O4@SiO2 nanoparticles through a layer‐by‐layer assembly. The structure of hybrid nanoparticles was characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, energy‐dispersive X‐ray spectroscopy, inductively coupled plasma atomic emission spectroscopy, vibrating sample magnetometry, Brunauer–Emmett–Teller surface area analysis, scanning electron microscopy, and transmission electron microscopy. Zinc‐poly(urea‐formaldehyde) supported on magnetic nanoparticles (MNPs@SiO2@PUF@Zn) was successfully used for the synthesis of spirooxindolopyran and spirooxindoloxanthene derivatives in aqueous medium as an environmentally benign condition. High yields, short reaction times, green solvent, reusability without significant reduction in catalytic activity, and simple separation of the catalyst using an external magnet along with environmental compatibility are some benefits of this procedure.

Synthetic strategies of heterocycle-integrated pyridopyrimidine scaffolds supported by nano-catalysts

“…Consequently, nano-catalysts recently are being widely applied for the construction of compounds with a pyrimidine skeleton. [140][141][142][143][144] Thus, consideration should be given to the productivity of the nano-catalyst relative to other catalysts, and the preparation of nanocatalysts at a lower cost. On the other hand, the ease of nanocatalyst preparation, and its separation from the reaction mixture to be recycled should be considered.…”

Recent trends in synthetic strategies using magnetic nanostructures as green catalysts in synthesis of pyran analogues

“…Bodaghifard and co‐workers [ 67 ] fabricated hybrid organic–inorganic nanostructure CoFe 2 O 4 @‐SiO 2 @PUF@Zn (OAc) 2 by immobilization of zinc acetate on the exterior of poly (urea‐formaldehyde), sustained on CoFe 2 O 4 @SiO 2 MNPs by layer‐by‐layer association ( Scheme 21 ) . The authors also employed zinc‐poly (urea‐formaldehyde) held by MNPs (MNPs@SiO 2 @PUF@Zn) to effectively synthesize spirooxindolopyran derivatives by reacting isatin derivatives with malononitrile in an ecologically benign aqueous medium condition ( Scheme 22 ) .…”